When used without a qualifier,
generally refers to crunching of a file using a particular C
implementation of compression by Joseph M. Orost et al. and widely
circulated via Usenet; use of crunch itself in this sense
is rare among Unix hackers. Specifically, compress is built around
the Lempel-Ziv-Welch algorithm as described in "A Technique for
High Performance Data Compression", Terry A. Welch, "IEEE
Computer", vol. 17, no. 6 (June 1984), pp. 8-19.